A coffee beverage, which is very popular and favorite drink, is usually produced by blending a coffee extract solution therein. Taste and flavor of a coffee beverage includes sweetness, acidity, bitterness, body, rich taste and unpleasant taste or the like. These tastes and flavors are characterized by roasted coffee beans, etc. used for producing a coffee extract solution. Furthermore, the taste and flavor of a coffee beverage vary depending upon the production country of coffee beans and the roasting method. Therefore, different types of roasted coffee beans are blended to obtain desired taste and flavor.
Furthermore, to enhance rich taste and body of a coffee extract solution, a method of adding a flavor improver to the coffee extract solution is proposed (Patent Documents 1 and 2).